Develop a Next.js page that uses the App Router and adheres to strict RSC patterns. Ensure client components are marked with 'use client' only when necessary, implement protected (auth) route groups, and configure server actions for form submissions with environment variable validation. Use the Next.js App Router exclusively with strict React Server Component (RSC) patterns. Mark client components with the 'use client' directive only when interactivity or hooks are needed. Implement route groups (such as (auth) and (public)) to distinguish protected routes, use server actions with form state helpers for backend logic, and configure environment variables in your next.config.mjs using schema validation.